I. Field of the Invention
The present invention relates generally to a crankshaft with a counterweight and, more particularly, to such a crankshaft with a laminated counterweight.
II. Description of the Prior Art
In a conventional crankshaft, the crankshaft includes a segmented main shaft having an axis aligned with the axis of rotation of the crankshaft. One or more crankpins are also provided at a position radially spaced but parallel to the main shaft. A piston is then secured to each crankpin in order to rotatably drive the crankshaft about its axis of rotation.
Since the crankpins are radially offset from the axis of rotation of the crankshaft, counterweights are conventionally provided for securing the main shaft to the crankpins so that the overall crankshaft has a balanced rotation. Such counterweights are typically made of a single heavy body of metal which is machined so that the crankshaft, including the main shaft segments and crankpins, is of a one-piece construction. Machining such crankshafts, however, is necessarily expensive which increases the overall cost of the crankshaft.
There have, however, been previously known crankshafts which utilize laminated counterweights so that the overall crankshaft is of a multi-piece construction. Such a laminated counterweight, which reduces the overall cost of the crankshaft, is disclosed in U.S. Pat. No. 4,342,236 to Everts which issued on Aug. 3, 1982.
These previously known crankshafts with laminated counterweights, however, merely duplicate the shape of the counterweight with the laminations. As such, the laminations are substantially triangular in shape with an opening for the main shaft segment extending through the center of the triangle and an opening for the crankpin provided at an apex of the triangle.
Since these previously known crankshafts with laminated counterweights merely duplicate the overall shape of the conventional one-piece counterweight, the volume of the crankcase for the engine remains substantially the same regardless of whether a one-piece counterweight is used or a laminated counterweight is used. Furthermore, reduction in the overall volume of the crankcase would advantageously result in the overall reduction of emissions of noxious fumes from the engine, especially for two-cycle engines.